This invention relates to a method for separating and recovering 4,4'-methylene dimethyl diphenyldicarbamate. More particularly, this invention relates to a method for separating and recovering substantially pure 4,4'-methylene dimethyl diphenyldicrbamate from a mixture of compounds including other methylene dialkyl diphenyldicarbamates, alkyl phenylcarbamates, higher phenylcarbamate derivatives, and related compounds.
The compound 4,4'-methylene dimethyl diphenyldicarbamate, hereinafter referred to as 4,4'-MDDC, which is an intermediate in the production of 4,4'-methylene diphenyldiisocyanate, hereinafter referred to as 4,4'-MDI, can be made by the condensation reaction of formaldehyde and methyl phenylcarbamate, hereinafter referred to as MPC. The 4,4'-MDDC can then be thermally decomposed to produce 4,4'-MDI, which is a particularly useful intermediate in the production of polyurethanes. It is accordingly important to provide a method of separating relatively pure 4,4'-MDDC from byproducts and intermediates of the condensation reaction and from unreacted MPC. The present invention provides such a method.